1. Field of the Invention
The present invention relates generally to pressure vessels for cryogenic fuels, and more particularly to a method for joining together structural components comprised of composite material using metal splicing members.
2. Description of the Related Art
Until recently, most pressure vessels were comprised of structures made of metals or metallic compounds. Techniques for securing together segments of such pressure vessels typically involved mechanical devices or bonding material, or a combination of the two. For example, U.S. Pat. No. 5,338,383 to Polackowyj teaches securing an insulation lining to a pressure vessel using mechanical fasteners, such as rivets, pins, clamps and the like, or bonding material, or both. Further, U.S. Pat. No. 2,925,193 to Gibb shows the use of mechanical fasteners to secure together stave elements made of reinforced, synthetic, resin materials
Not until recently, however, has the use of non-metallic materials for fabricating pressure vessels been implemented. The development of such new materials was principally occasioned by efforts to find improved ways for exploring space through research directed at discovering of new modes of transportation for high speed space travel, and new fuels or propellants systems, such as cryogenic fuels or propellants. One important discovery has been the versatility of composite material systems, not only for vehicle structures, but also for subsystems in such vehicles.
An area of application for composite material systems, whether or not reinforced, is in fuel containment applications. Composite materials are significantly lighter in weight than metal counterparts, are non-corrosive, and exhibit the same, if not significantly higher, strength. Typically, these tanks are pressurized, and are not depressurized until the propellant has been used up. For use in spacecraft, such tanks must be able to withstand the high internal pressures for long periods of time without leaking. One place where leaks tend to occur in fuel tank applications is in the vicinity of the connection between the tank components, such as at seams or joints.
The minimization of process time for manufacture of such structures is always of high priority. The use of "green" uncured composite materials for pressure vessels permits ease of manipulation of materials, sometimes by hand, to achieve oftentimes very involved configurations. After a shape or contour has been imparted to the green material, curing is generally carried out to obtain rigid, very strong, unitary structures.
Against this background of known technology, the applicants have developed novel methods for joining sections of vessels designed for containment of pressurized cryogenic fuels. Applicants also discovered that, by using these methods for joining vessel sections together, a new and significantly improved fuel containment pressure vessel is obtained.